“Instead of saying she’d lost her youth, he said she was ‘surprised by time’. I’d been reading his biography the night before making my 80th birthday speech, so I used it.” Longevity can be good for artists, providing perspective, experience and the sort of explosion of creativity Picasso enjoyed at the end of his life.

This rule certainly applies to Ireland’s most important landscape painter, the man who has put counties Fermanagh and Sligo on the creative map as Paul Henry did 100 years ago with Donegal.

TP Flanagan, Terry to his many friends, may have turned 80 in March, but his enthusiasm for life, art, discussion and Choco Leibniz biscuits is undimmed.

Now busy with a couple of exhibitions, one that has just opened at the Ormeau Baths Gallery in Belfast and another in Banbridge in August, Flanagan admits he hasn’t altered his lifelong habit of planning blocks of work.

“I work in themes and like to see how one painting will fit in with the next. The Ormeau Baths show involves my earlier work and is about the way the Troubles affected me. Liam Kelly organised it with my son Philip and they showed me a visual diary of my paintings.”

In a super-sunny conservatory off the Flanagans’ large BT9 house, he adds: “In retrospect, I can see how the Troubles must have had an effect on every creative artist, direct or indirect.

“I am a visual artist and thought that the new medium, television, was presenting fantastic images of what was happening, so it wasn’t a painter’s obligation to record that. But one of my series of works was called A Frozen Lake, and I felt that we were frozen into attitudes.” Included in the Belfast exhibition are other striking pictures that seem to symbolise Ulster’s pain, including Victim and A Rose Wrapped Up.

Although he is serious about serious matters, there’s an aura of good humour when you’re in Terry Flanagan’s company. He readily accommodates the photographer by posing in his eyrie-like studio on the third floor. As we reach it, passing a deal of interesting objects on the way, he says contentedly: “This is where we hang out.”

On old age, he is philosophical. “I think you seldom realise what age you are. As I don’t paint pictures in isolation, I like to look ahead. Now I’m 80 I do sometimes think ‘If it takes me five years to finish that series, I may not be around long enough.’” He laughs.

Set on the easel is a characteristically loose yet sophisticated account in oils of Reflections of Lower Lough Erne.

“I don’t know whether it’s finished or not. Sometimes I live with a painting for a wee while to make up my mind.”

Terry Flanagan gamely puts some red paint on his palette and adopts the painter’s pose. When I suggest the addition of red might recall Constable, he says: “This doesn’t need any red, but Paul Henry always had a touch of red, in a petticoat or something.”

The studio with its massive window is where TP Flanagan produces most of his work: “It’s where I am not disturbed and has good light. There’s a tradition that an artist must have north light, but I don’t care where it comes from, and the first light I get is from the east”.

After submitting to another photo in the conservatory, and producing a nice Ian Paisley anecdote, the artist chats about his support system, in other words his family.

Catherine Flanagan, his daughter and another artist, provides an insight into growing up with an artist father — “I think there is a family connection in our work, we all grew up watching daddy paint” — while his wife Sheelagh rustles up excellent coffee. TP has three grown-up children, Philip, Catherine and Tony.

A bit of a romantic, Terry Flanagan says that his early oil painting of fir tree branches, placed next to a contemporary study in pink and black by his son Philip, is one of his favourites because it dates from the middle 1950s when he was courting Sheelagh.

“We married in 1959, but I originally met Sheelagh through the Lyric Theatre. She was very keen on acting, and had done part-time work in sound radio.

Mary O’Malley of the Lyric was a great woman at finding out what people could do, then using them.

She discovered I was an artist and got me to paint sets. The cast were rehearsing a Christmas play, Synge’s Riders to the Sea, plus a Lorca, The House of Bernarda Alba, which Sheelagh was in.

“Once we realised we were both interested, I painted more sets willingly.” At that period, Sheelagh had a flat in Mount Charles, while TP Flanagan was living off Botanic Avenue. “I often picked her up from the theatre and took her home.”

The Flanagan style often involves very free brushstrokes and in his approach to his main subject — Northern Irish landscapes where, as his friend Seamus Heaney put it, there’s a flirtation between land and water — Flanagan sometimes veers towards abstraction. His Dawn at Fermanagh Lough is one sensuous example, but Flanagan doesn’t entirely agree with the theory. “I never consciously say ‘I’m going to paint an abstract picture.’ You spend a certain period arranging the motifs and managing shapes. If you take a sense of narrative and content out, you get abstractions. But there’s no such thing as a totally abstract or totally narrative painting.” After touching on late Turner, who did get pretty abstract at the end, I gain the background to further works of art littering the Flanagans’ slightly bohemian Victorian semi. There are primitive portraits of sheep and handsome sculptures by Philip Flanagan, now carving out a significant career in London.

The Flanagans’ second son, Tony, is an archaeologist. Is Mr Flanagan pleased at having founded an artistic dynasty ? “I’m sort of sorry for them and glad for them at the same time, if you’re talking about the financial side. The people my son went to college with, who did law or medicine, are earning much more. Young artists have a rough time.”

Now a TP Flanagan canvas commands up to several thousand pounds and his work is in many collections, including the Museum of Modern Art, Dublin, the Ulster Museum and Queen’s. When a painting or batch of paintings is finished, he habitually offers his wife first choice. “Sheelagh’s got a good collection of my work.”

The rest are sold, a process he doesn’t find particularly depressing.

“I’m sometimes relieved to see them go. You can’t paint in a vacuum, it’s all to do with communication. The work contains enlightenment and you want to pass it on.” He adds that it’s a bit like a woman having a baby.

One result of producing so much excellent art is TP Flanagan’s honorary doctorate, awarded him by Queen’s University last week. But the new title isn’t going to go to his head. “I won’t go around calling myself Doctor, and I wouldn’t want to sign a painting Dr TP, although I suppose I might put it on the back. These sorts of things are archived,

they’re for the people who come along afterwards.”

That is important, as Flanagan’s place in the Irish artistic pantheon is secure. The man is embedded in Northern Irish cultural life like the bones of Ulster landscape in his art.

Terry’s stories are entertaining. He talks about holidaying in Donegal with the Heaneys when both men had young families.

“At about three thirty to four in the afternoon, there’d be a family tea for the mothers and young children. Seamus and I and the other husbands would get in the car and beat off far from the scene and end up driving round Bloody Foreland. The landscape was mountain and bog trembling under the sky and Seamus said ‘We’re on top of something that goes way way down.’”

This is the landscape that Flanagan painted so memorably in his dark, energetic work Boglands, that also produced Heaney’s poem with its goosebump-inducing last line ‘The wet centre is bottomless.’ Although this is a notable artistic double act, it was totally spontaneous. “I didn’t say to Seamus, ‘Oh, I’m going home and making a picture.’” the artist says with a smile. Then Terry Flanagan adds a neat insight into the great poet’s methods. “Sometimes if we’re out in his car in Co Wicklow, Seamus will begin to tap the steering wheel, lightly tapping. And you think he’s got the rhythm of a poem.”

Waiting for the taxi, I’m ushered into a sitting room with wall-to-wall Flanagans, and the conversational ping-pong turns to the difference between paintings and photographs. Flanagan points out that an artist may move a tree to get the right effect, and insists on the “primacy of imagination”.

Surprised by time? Entertained, more like.

Correspondences, a show of TP Flanagan’s work, runs at the Ormeau Baths Gallery (9032 1402) until July 17. A TP Flanagan exhibition runs at the FE McWilliam Gallery, Banbridge (028 4062 3322) from August 28-October 31